Infantile Blount's Disease (tibia vara)

Author: Chris Souder

Topic updated on 02/21/13 7:31am

Introduction

Blount's disease is progressive pathologic genu varum centered at the tibia
Best divided into two distinct disease entities
- Infantile Blount's (this topic)
  - pathologic genu varum in children 0-3 years of age
  - more common
  - typically affects both lower extremities
- Adolescent Blount's
  - pathologic genu varum in children > 10 years of age
  - less common
  - less severe
  - more likely to be unilateral
Etiology
- likely multifactorial but related to mechanical overload in genetically succeptible individuals including
  - excessive medial pressure produces an osteochondrosis of the medial proximal tibial physis and epiphysis
    - osteochondrosis can progress to a physeal bar
Risk factors
- overweight children that are early walkers (less than one year)
Prognosis
- best outcomes are associated with early diagnosis and unloading of the medial joint with either bracing or an osteotomy
Differential diagnosis
- the following conditions can also lead to pathologic genu varum
  - osteogenesis imperfecta
  - osteochondromas
  - trauma
  - various dysplasia

Anatomy

Genu varum is a normal physiologic process in children
- physiologic genu varum
  - genu varum (bowed legs) is normal in children less than 2 years
  - genu varum migrates to a neutral at ~ 14 months
  - continues on to a peak genu valgum (knocked knees) at ~ 3 years of age
  - genu valgum then migrates back to normal physiologic valgus at ~ 4 years of age

Classification

Langenskiold Classification
- type I thru IV consist of increasing medial metaphyseal beaking and sloping
- type V and VI have an epiphyseal-metaphyseal bony bridge (congenital bar across physis)
- provides prognostic guidelines

Presentation

Physical exam
- genu varum deformity
  - usually bilateral in infants
- often associated with internal tibial torsion

Imaging

Radiographs
- views
  - ensure that patella are facing forwards for evaluation (commonly associated with interal tibial torsion)
- findings suggestive of Blounts disease
  - varus focused at proximal tibia
  - severe deformity
  - asymmetric bowing
  - progressing deformity
  - sharp angular deformity
  - lateral thrust during gait
  - metaphyseal beaking
    - different than physiologic bowing which shows a symmetric flaring of the tibia and femur
- measurements
  - metaphyseal-diaphyseal angle (Drennan)
    - angle between line connecting metaphyseal beaks and a line perpendicular to the longitudinal axis of the tibia
    - >16 ° is considered abnormal and has a 95% chance of progression
    - <10 ° has a 95% chance of natural resolution of the bowing
  - tibiofemoral angle
    - angle between the longitudinal axis of the femur and tibia

Treatment

Nonoperative
- brace treatment with KAFO
  - indications
    - children < 3 years (especially if unilateral)
    - Stages I-IV
  - outcomes
    - poor results associated with obesity and bilaterality
    - if successful, improvement should occur within 1 year
    - bracing must continue for approximately 2 years for resolution of bony changes
Operative
- proximal tibia/fibula valgus osteotomy
  - indications
    - children > 3 years
      - risk of recurrence is significantly lessened if performed before 4 years of age
    - stages V and VI
    - failure of brace treatment

Surgical Techniques

Proximal tibia/fibula valgus osteotomy
- goals of correction
  - overcorrect into 10-15° of valgus because medial physeal growth abnormalities persist
  - distal segment is fixed in valgus, external rotation and lateral translation
- technique
  - staples and plates function by increasing compression forces across the physis which slows longitudinal growth (Heuter-Volkman principle)
  - temporary lateral physeal growth arrest with staples or plates can be used
    - increasing use for correction in younger patients
  - include a bar resection (epiphysiolysis) when a physeal bar is present (Langenskiold V and VI)
    - consider hemiepiphysiodesis if bar > 50%
  - medial tibial plateau elevation is required at time of osteotomy if significant depression is present
  - consider prophylactic anterior compartment fasciotomy

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Qbank (4 Questions)

TAG

(OBQ08.124) A 32-month-old male with severe infantile Blounts disease has been treated with full time bracing for the past year. At most recent follow-up, the varus deformity of his bilateral legs has worsened despite compliance with bracing. What treatment is now recommended? Topic

Review Topic

1. Observation, discontinuation of bracing
2. Observation, continuation of full-time bracing
3. Bilateral proximal tibial osteotomies
4. Bilateral distal femur osteotomies
5. Bilateral proximal tibial medial hemiepiphysiodesis

PREFERRED RESPONSE ▶

DISCUSSION: Infantile Blount’s disease is a pathologic type of tibia vara which develops in children 0-4 years of age. Bracing is indicated in patients < 3 years of age with Langenskiöld stage I-II disease, and is more effective in patients with unilateral disease. Surgery is indicated if varus secondary to Blount's disease persists at the age of 4 or if bracing fails in 2-3 year olds after 12 months (answer 3). Correction is achieved surgically with a proximal tibial realignment osteotomy. Answer 5 is incorrect because closing down the medial side will cause further varus. Answer 4 is wrong because the pathology is in the tibia and not the femur in infantile blount’s. The cited paper by Feldman discusses the two options of acute vs gradual correction of tibia vara. They concluded that gradual correction is a more accurate treatment in regards to correction of the limb length inequality, mechanical axis deviation, and medial proximal tibial angles. While there is literature to support the use of guided-growth in patients with adolescent Blount's, further investigation is required to see if similar results can be obtained in patients with infantile Blount's.

REFERENCES:

1. Feldman DS, Madan SS, Ruchelsman DE, Sala DA, Lehman WB. Accuracy of correction of tibia vara: acute versus gradual correction.J Pediatr Orthop. 2006 Nov-Dec;26(6):794-8. PMID:17065949 (Link to Abstract)

2. Dormans. Core Knowledge in Orthopaedics: Pediatric Orthopaedics. p201-202

Question Authors:

Chris Souder MD, Patrick McCulloch MD, Eric Shirley MD,

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TAG

(OBQ08.183) In the treatement of Blount's disease, how do plates or staples help correct the genu varum deformity? Topic

Review Topic

1. Increasing compression forces across the physis to slow longitudinal growth
2. Decreasing compression forces across the physis to slow longitudinal growth
3. Increasing tension forces across the physis to slow longitudinal growth
4. Decreasing tension forces across the physis to slow longitudinal growth
5. Increasing shear forces across the physis to slow longitudinal growth

PREFERRED RESPONSE ▶

DISCUSSION: Increasing compression forces across the physis in the form of plates or staples will slow longitudinal growth.

Blount’s disease, also called tibia vara, is the most common cause of genu varum that is not physiologic. The pathoanatomy is thought to involve excessive medial pressure (eg, heavy, early walkers who are in physiologic varus alignment) that produces an osteochondrosis of the physis and adjacent epiphysis that can progress to a complete physeal bar. The Hueter-Volkmann law states that increasing compression across a growth plate leads to decreasing growth and increasing tension stimulates growth.

Sabharwal presents a Level 5 review stating that in addition to tibia vara, Blount's disease is also characterized by tibia procurvatum, internal torsion, and limb shortening. Additionally, distal femoral varus is commonly noted in the late-onset form.

Moen and Pelker performed a biomechanical investigation on bovine femora. They found that the zone of provisional calcification and the metaphysis failed when subjected to compression forces.

Illustration A shows the histologic zone of failure varies with the type of load applied to the specimens.

Illustrations: A

REFERENCES:

1. Sabharwal, Sanjeev. Blount disease.J Bone Joint Surg Am. 2009 Jul;91(7):1758-76 PMID:19571101 (Link to Abstract)

2. AAOS Comprehensive Orthopedic Review, Editor Jay Lieberman, AAOS, 2009 (Chapter 4, IV)

3. Moen CT, Pelker RR: Biomechanical and histological correlations in growth plate failure. J Pediatr Orthop 1984;4:180-184 PMID:6199372 (Link to Abstract)

Question Authors:

Doug Nowak MD, Patrick McCulloch MD, Michael Hughes MD,

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TAG

(OBQ05.23) A 30-month-old boy has worsening bilateral bowleg deformities, and radiographs are shown in Figure A. The most appropriate initial management should consist of which of the following? Topic

Review Topic

FIGURES: A

1. Observation
2. Full-time bracing with knee-ankle-foot orthoses
3. Night-time bracing with knee-ankle-foot orthoses
4. Proximal tibia/fibula valgus osteotomy with bar resection
5. Proximal tibia/fibula valgus osteotomy with hemiepiphysiodesis

PREFERRED RESPONSE ▶

DISCUSSION: Initial management of infantile Blount's disease in children less than 3 years old consists of full time bracing with a knee-ankle-foot orthosis.

Infantile Blount's disease is pathologic cause of genu varum in children less than 3 years of age. Radiographically, a widened and irregular medial physeal line and an irregularly ossified and medially sloped epiphysis are seen. Initial treatment is non-operative in children less than 3 years of age. Operative management in children older than 3 is considered if non-operative management has failed, or in Langenskiold classes V and VI, where there is a congenital bar across the physis. When osteotomy is required, overcorrection to at least 5 degrees of valgus should be done.

Richards et. al. reported successful outcomes following bracing for an average of 9 months in patients 3 years and younger with Langenskiold stage II or less. Patients with bilateral disease more commonly required osteotomy.

Figure A shows bilateral infantile Blount's disease, with varus angulation of the tibial metaphysis and beaking of the medial metaphysis.

REFERENCES:

1. Richards BS, Katz DE, Sims JB: Effectiveness of brace treatment in early infantile Blount’s Disease. J Pediatric Orthop 1998;18:374-380. PMID:9600567 (Link to Abstract)

2. Herring JA: Disorders of the leg, in Herring JA (ed): Tachdijian’s Pediatric Orthop, Ed. 3. Philadelphia, PA, WB Saunders, 2002, pp 839-890.

Question Authors:

Ben Taylor MD, Jan Szatkowski MD, Michael Hughes MD,

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Videos

Bow Legs In Children - Everything You Need To Know - Dr. Nabil Ebraheim

Pediatrics - Educational Presentation - Infantile Blount's Disease (tibia vara)

Educational video describing the condition of bow leg in children.

11/5/2012

339 views

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Accuracy of Correction of Tibia Vara: Acute versus Gradual Correction. Includes Poll

Feldman DS, Madan SS, Ruchelsman DE, Sala DA, Lehman WB
J Pediatr Orthop. 26(6):794-8. PMID: 17065949 (Link to Pubmed)

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Evidence & References Show References

Level of Evidence 3 (Retrospective Cohort Study or Case-Control Study)

Richards BS, Katz DE, Sims JB: Effectiveness of brace treatment in early infantile Blount’s Disease. J Pediatric Orthop 1998;18:374-380. PMID:9600567 (Link to Abstract)

Level of Evidence 5 and Other Journal Articles (includes Case Reports, Expert Opinions, Personal Observations, and Biomechanic Studies)

Moen CT, Pelker RR: Biomechanical and histological correlations in growth plate failure. J Pediatr Orthop 1984;4:180-184 PMID:6199372 (Link to Abstract)
Sabharwal, Sanjeev. Blount disease.J Bone Joint Surg Am. 2009 Jul;91(7):1758-76 PMID:19571101 (Link to Abstract)

Textbooks

Review of Orthopaedics, 6th Edition, Mark D. Miller MD, Stephen R. Thompson MBBS MEd FRCSC, Jennifer Hart MPAS PA-C ATC, an imprint of Elsevier, Philadelphia, Copyright 2012
AAOS Comprehensive Orthopaedic Review, Jay R. Leiberman. Published by American Academy of Orthopaedic Surgeons, Rosemont IL. Copyright 2009
Orthopaedic Knowledge Update 10, John M Flyn. Published by American Academy of Orthopaedic Surgeons, Rosemont IL. Copyright 2011
Hoppenfeld SP. Surgical Exposures in Orthopaedics: The Anatomic Approach. Lipponcott, Williams, and Wilkins, Philadelphia, PA, Copyright 2009
Orthopaedic In-training Examination (OITE) Questions 2004-2012, American Academy of Orthopaedic Surgeons, Rosemont IL. Copyright 2004-2012
Self-Assessment Examination (SAE) Questions 2004-2012, American Academy of Orthopaedic Surgeons, Rosemont IL. Copyright 2004-2012
AAOS Comprehensive Orthopedic Review, Editor Jay Lieberman, AAOS, 2009 (Chapter 4, IV)
Herring JA: Disorders of the leg, in Herring JA (ed): Tachdijian’s Pediatric Orthop, Ed. 3. Philadelphia, PA, WB Saunders, 2002, pp 839-890.

Undefined

Dormans. Core Knowledge in Orthopaedics: Pediatric Orthopaedics. p201-202
Feldman DS, Madan SS, Ruchelsman DE, Sala DA, Lehman WB. Accuracy of correction of tibia vara: acute versus gradual correction.J Pediatr Orthop. 2006 Nov-Dec;26(6):794-8. PMID:17065949 (Link to Abstract)
Loder RT, Johnston CE 2nd. Infantile tibia vara. J Pediatr Orthop. 1987 Nov-Dec;7(6):639-46. PMID:3429646 (Link to Abstract)
Raney EM, Topoleski TA, Yaghoubian R, Guidera KJ, Marshall JG. Orthotic treatment of infantile tibia vara. J Pediatr Orthop. 1998 Sep-Oct;18(5):670-4. PMID:9746423 (Link to Abstract)

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Infantile Blount's Disease (tibia vara)

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